In a vehicle such as an automobile, an intake manifold is attached to an engine. Japanese Patent Application Laid-Open No. 2016-70249 discloses an intake manifold including a runner connected to a cylinder head of an engine, a surge tank connected to an intake upstream side of the runner, and a throttle valve passage connected to an intake upstream side of the surge tank for taking in fresh air. Then, in the intake manifold disclosed in Japanese Patent Application Laid-Open No. 2016-70249, a throttle valve is attached to an intake upstream end of the throttle valve passage.
Some of conventional intake manifolds adopt a configuration in which an EGR (Exhaust Gas Recirculation) passage for introducing an EGR gas is connected to a throttle valve passage. According to conventional art, an EGR passage is connected to a part immediately downstream side of a throttle valve on a throttle valve passage.
As described above, connecting the EGR passage to a part immediately downstream side of the throttle valve on the throttle valve passage enables an EGR gas to be taken into the throttle valve passage smoothly making use of a negative pressure generated immediately downstream side of a valve body in the throttle valve.